This invention relates to an apparatus for processing information carried by an electro-magnetic radiation beam to record the information on a specific recording apparatus as a charge latent image and reproduce the information by means of an electro-magnetic radiation beam such as light.
There is a conventional apparatus for recording/reproducing information such as a graphic image in the form of a charge latent image as shown in FIGS. 1 and 2. FIGS. 1 and 2 depict a recording system and a reproducing system, respectively.
Throughout the drawings, like reference numerals and letters are used to designate like or equivalent elements for the sake of simplicity of explanation.
First, the recording system will be explained with reference to FIG. 1. In FIG. 1, a recording medium 10 on which a charge latent image is intended to be recorded is composed of a charge holding layer (hereinafter abbreviated CHL) member 12 and a transparent electrode 14. A photoelectric recording head 16 is composed of a photoconductive layer (hereinafter abbreviated PCL) member 18 and a transparent electrode 20.
The recording medium 10 and the photoelectric recording head 16 are arranged such that the CHL member 12 and the PCL member 18 face each other across a predetermined space. The light carrying the optical image of an object O is allowed to be incident to the transparent electrode 20 of the photoelectric recording head 16 through an imaging lens 22, as depicted by an arrow A10.
A d.c. power supply 26 is connected across the electrodes 14 and 20 through a switch 24. There will be a discharge generated across the CHL member 12 and the PCL member 18 by turning on the switch 24.
In the configuration, the CHL member 12 is to hold charges for a long period of time and is formed of a material having extremely high insulation resistance, such as silicon resin. While, the PCL member 18 is to generate electron-hole pairs and is formed of, for example amolphous silicon. In FIG. 1, the electrons are transferred to the transparent electrode 20 side in the PCL member 18, whereas, the holes are transferred to the side in the layer 18, facing the CHL member 12. The electrodes 14 and 20 are formed of a material such as ITO (Indium Tin Oxide).
The recording operation of the recording system constituted as described above will now be explained. As is depicted by the arrow A10, the light carrying the optical image of the object O is incident to the imaging lens 22 and is further incident to the PCL member 18 of the photoelectric recording head 16, through the imaging lens 22 and the transparent electrode 20. The light is then absorbed in the PCL member 18 to generate the electron-hole pairs therein.
Now the switch 24 is turned on to allow the power supply 26 to apply a voltage across the electrodes 14 and 20. This causes the electrons in the PCL member 18 being attracted by the positive polarity of the power supply 26 to be transferred to the transparent electrode 20 side, while the holes are transferred to the side of the layer 18, facing the CHL member 12, as described above. The holes or the positive charge image corresponding to the optical image of the object O are therefore formed on the surface of the PCL member 18, facing the CHL member 12.
Furthermore, there is a discharge generated across the PCL member 18 and the CHL member 12 due to the voltage applied by the power supply 26. This discharge causes electrification on the surface of the CHL member 12 facing the PCL member 18, so that charges Q are stored thereon.
The electrification due to the discharge depends on the distribution of the holes or the positive charge image on the surface of the PCL member 18. The charge latent image corresponding to the optical image of the object O is thus transferred to the surface of the CHL member 12. Since the switch 24 causes the formation of the charge latent image, the switch 24 may be applied to a shutter of a camera.
Next, the reproducing system will be explained with reference to FIG. 2. In FIG. 2, there is arranged an optical reproducing head 28 facing the recording medium 10 on which the charge latent image has been recorded. The optical reproducing head 28 is composed of a photo-modulation layer (hereinafter abbreviated PML) member 30 and a transparent electrode 32. The surface of the PML member 30 faces the CHL member 12 of the recording medium 10, in the configuration. An optical reading unit 34 is further arranged to emit a reading light to the transparent electrode 32 of the optical reproducing head 28 as depicted by an arrow A12. The reading light passing through the optical reproducing head 28 and the recording medium 10 is allowed to be incident to a photo-detection unit 36 as depicted by an arrow A14.
In the configuration, PML member 30 of the optical reproducing head 28 is formed of a material such as LiNbO.sub.3, BSO (Bi.sub.12 SiO.sub.20), liquid crystal, PLZT (Lead lanthanum zirconate titanate) or EC (Electrochromic), having the photoelectric effect that light is varied according to the electric field. The photoelectric effect may be a double reflection effect, scattering effect or coloring effect. Selection of the material thus depends on the purpose. The optical reading unit 34 is composed of a laser light source, a polarizer, etc. (not shown), to generate the light for reading the charge latent image. The photo-detection unit 36 is further composed of a wave-plate, an analyzer, a photoelectric convertor, etc. (not shown), to detect the light incident thereto.
The operation of the reproducing system will now be explained. The charge latent image corresponding to the object O has already been recorded on the recording medium 10 as described with reference to FIG. 1. The optical reproducing head 28 is arranged adjacent to the recording medium 10 and the transparent electrodes 14 and 32 are electrically connected to each other. In this configuration, the electric field due to the latent charges Q will affect the PML member 30 to cause an electro-optic effect in the incident light.
Now the optical reading unit 34 emits the reading light to the optical reproducing head 28 to force the PML member 30 to cause the electro-optic effect. The phase of the light emitted to the PML member 30 and that of the light subjected to the electro-optic effect therein are therefore varied with respect to each other.
The reading light subjected to the electro-optic effect passes through the recording medium 10 and is incident to the photo-detection unit 36. The intensity distribution of the reading light is varied accordingly with the distribution of the latent charges Q by the analyzer (not shown) and is converted to elecric siganls. As a result, the electric signals corresponding to the optical image of the object O are generated.
However, in the case of color image photographing by means of the conventional apparatus as described above, the light from the object O should be separated into primary colors by proper optical equipment, to be recorded, reproduced and combined with each other.
The conventional charge latent image recording/reproducing apparatus as described above has drawback that color superposition and color separation cannot be easily performed for its complex configuration.
Next, as for a conventional apparatus having a filter composed by arranging, with a specific order, a plurality of filter elements with different characteristic from each other, through which electro-magnetic radiation beams with specific and different ranges of wave length pass respectively, a color separation stripe filter F, as shown in FIG. 3A, composed by arranging a plurality of color stripe filter elements with different characteristics from each other is provided along an optical passage to an imaging device for generating a color superimposed signal.
The color separation stripe filter F shown in FIG. 3A is composed by arranging a color stripe filter R allowing red light R, G green light and B blue light to pass through a specific repeating order. Therefore, when an electron beam scans a photoelectric conversion section of an imaging device onto which an optical image passing through the filter F is projected, the imaging device generates a signal which is separated by the filter F, such as the signal shown in FIG. 3B that red, green and blue signals are each arranged on the time domain with a specific repeating order. The signal thus separated is the color-separated signal, as shown in FIG. 4, which is composed of a low-frequency component of the red, green and blue signals (the signal component existing in the region depicted by a solid line in FIG. 4) and a modulated signal component which is a carrier with a frequency f, corresponding to the repeating order of the color stripe filters of the color separation filter F, is amplitude modulated with the red, green and blue signals (the signal component existing in the region depicted by a dashed line.).
The conventional apparatus has the drawback that the color-superimposed signal generated by the conventional apparatus as described above is subjected to the quality of an optical system of the apparatus and the resolution of the imaging device thereof. Other than that, a demodulation means is required for obtaining three primary color signals from the superimposed signal, the signal-to-noise ratio (S/N) is degraded since the demodulated signal exists in the high-frequency range and the like.
Furthermore, since information is processed in the form of an electric signal conventionally, a signal processing circuit is required for each of the primary three colors which are to be processed by gamma correction or other signal processings. For that reason, the conventional apparatus is made complex for signal processing.